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# Empirical formula confusion... watch

1. The question states: an oxide of sulphur contains 50% sulphur and 50% oxygen by mass. Work out it's empirical formula.
I am confused about what they mean by an oxide of sulphur. Is it sulphur dioxide? So do I work out the mass of that compound and then go from there? Or is something else meant by 'an oxide of sulphur'. Is it sulphur oxide?
2. I guess that the aim of the question is to get you to figure out what oxide is meant. So you should figure out the ratio of the two atoms with the formula n=m/M, where you can substitute m for 5 or whatever you like as long as you use the same number for both substances.

So, if you were, for example, to get a result like n(S)=0,33 and n(O)=1, then you just multiply both numbers until you reach a whole number: in this example that would be n(S)=1 and n(O)=3, and from there you can work out that the oxide in question was SO3.

Hope this helps
3. (Original post by StationToStation)
I guess that the aim of the question is to get you to figure out what oxide is meant. So you should figure out the ratio of the two atoms with the formula n=m/M, where you can substitute m for 5 or whatever you like as long as you use the same number for both substances.

So, if you were, for example, to get a result like n(S)=0,33 and n(O)=1, then you just multiply both numbers until you reach a whole number: in this example that would be n(S)=1 and n(O)=3, and from there you can work out that the oxide in question was SO3.

Hope this helps
Sorry, I don't really understand what you mean. Could you paraphrase? Thank you...
4. (Original post by Wolfram Alpha)
Sorry, I don't really understand what you mean. Could you paraphrase? Thank you...
Oh, ok!

So I assume you know what an empirical formula is? It's the simplest possible ratio of different atoms in a compound. So, for example: for glucose, it's molecular formula is C6H12O6, and it's empirical formula is CH2O. So really the aim here is to figure out the number of Oxygen atoms in RELATION to the number of Sulphur atoms in the compound. You would get the same empirical formula for S2O4 and SO2.

Because of this we don't need to know the exact mass of both atoms; we only need to know the relation of the masses. Here, we know that since both substances account for 50% of the weight, they must weigh the same amount. We also know that the molar mass for Oxygen is 16 and for Sulphur 32.

We want to figure out the relation of the number of atoms, and since we know the molar masses and the relation of the weights, we can use the formula n=m/M, where n stands for moles, m stands for weight and M stands for molar mass. Since the weights are the same, we could decide to use the weight of 32 for both, which would make the calculations easier. This way we would get

n(O)= 32/16 = 2
n(S)= 32/32 = 1

And here we already have the relationship of the number of atoms in the simplest possible form. So, the empirical formula would thus be SO2.
5. (Original post by StationToStation)
Oh, ok!

So I assume you know what an empirical formula is? It's the simplest possible ratio of different atoms in a compound. So, for example: for glucose, it's molecular formula is C6H12O6, and it's empirical formula is CH2O. So really the aim here is to figure out the number of Oxygen atoms in RELATION to the number of Sulphur atoms in the compound. You would get the same empirical formula for S2O4 and SO2.

Because of this we don't need to know the exact mass of both atoms; we only need to know the relation of the masses. Here, we know that since both substances account for 50% of the weight, they must weigh the same amount. We also know that the molar mass for Oxygen is 16 and for Sulphur 32.

We want to figure out the relation of the number of atoms, and since we know the molar masses and the relation of the weights, we can use the formula n=m/M, where n stands for moles, m stands for weight and M stands for molar mass. Since the weights are the same, we could decide to use the weight of 32 for both, which would make the calculations easier. This way we would get

n(O)= 32/16 = 2
n(S)= 32/32 = 1

And here we already have the relationship of the number of atoms in the simplest possible form. So, the empirical formula would thus be SO2.
Ohhhhh! Yes I understand. I completely missed the implications of the weights being equal. Thanks very much for taking the time to explain this to me! I appreciate it very much .
6. (Original post by Wolfram Alpha)
Ohhhhh! Yes I understand. I completely missed the implications of the weights being equal. Thanks very much for taking the time to explain this to me! I appreciate it very much .
No problem, I'm glad I could help!

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